Collecting part structure of exhaust manifold

ABSTRACT

A collecting part structure of an exhaust manifold, in which connecting portions of branch pipes  2  to  5  to a head flange  1  are arranged on a straight line, has a reinforcement member that includes two flat plates  10  and  11  to collect and fix downstream side portions f the branch pipes  2  to  5.  The flat plates have the same length as an inner diameter of a collecting part  6,  and are formed at central positions thereof with slits S 1  and S 2  facing each other to be joined with each other like a cross shape. The flat plate  11  with the slit S 2  at an exhaust-gas upstream side, of the two flat plates  10  and  11,  is arranged on a line A 2  parallel to a line on which the connecting portions of the branch pipes  2  to  5  to the head flange 1 are arranged.

TECHNICAL FIELD

The present invention relates to a collecting part structure of anexhaust manifold that is connected with an engine of a motor vehicle orthe likes.

BACKGROUND OF THE INVENTION

A conventional collecting part structure of an exhaust manifold isdisclosed in Japanese Patent application Laid-Open Publication No.2003-83062. The conventional collecting part structure of the exhaustmanifold includes four branch pipes and a collecting part, whereexhaust-gas upstream side end portions of the branch pipes are connectedwith a head flange in line thereon, exhaust-gas downstream side endportions thereof are formed to have a cross section shaped like aquadrant circle, and the collecting part collects and contains theexhaust-gas downstream side end portions assembled to form a circularcross section. A reinforcement member is provided among the exhaust-gasdownstream side end portions, being fixed thereto. The reinforcementmember is constructed by two flat plates that are coupled like a crossshape by engaging slits formed on the flat plates, and it is arranged sothat the flat plates intersect in an oblique direction with a line onwhich collecting portion of the exhaust-gas upstream side end portionsof the branch pipes are aligned.

DISCLOSURE OF THE INVENTION Problem(s) to be Solved by the Invention

The conventional invention, however, needs to increase plate thicknessesof the flat plates of the collecting part or use expensive material forthe flat plate for the following reason. Stress concentration could havegenerated at the exhaust-gas downstream end portions of the branch pipesand their peripheral portions, being generated by stress due to thermalexpansion of the branch pipes and thermal stress due to thermalextension of the head flange in a longitudinal direction thereof. Inthis case, the flat plates are bent so that both upstream side endportions of the flat plates are not only bent in a width directionthereof so as to approach to each other, but also are twisted to departfrom each other in a reverse direction with respect to a thicknessdirection of the plates, respectively. This requires the flat platesthat have a larger plate thickness or are made of expensive material, inorder to ensure sufficient strength thereof.

The present invention is made to solve the above-described problem, andits object is to provide a collecting part structure of an exhaustmanifold that can easily increase the strength to resist stressconcentration at exhaust-gas downstream side end portions and theircircumferential portions of branch pipes.

Means for Solving the Problems

According to a first aspect of the present invention there is provided acollecting part structure of an exhaust manifold including four branchpipes, a collecting part and a reinforcement member. Exhaust-gasupstream side end portions of the four branch pipes are connected with ahead flange on a straight line, while exhaust-gas downstream side endportions thereof are formed to have a cross section of a quadrantcircle. The collecting part collects and contains the exhaust-gasdownstream side end portions of the branch pipes to form a circularcross section. The reinforcement member is disposed among theexhaust-gas downstream side end portions of the branch pipes to fix theexhaust-gas downstream side end portions to the collecting part, and thereinforcement member has two flat plates with the same length as aninner diameter of the collecting part. The flat plates are provided atcentral positions with slits facing to each other to be joined like across shape. One flat plate, of the flat plates, that is formed with aslit at an exhaust-gas upstream side thereof is arranged parallel withthe straight line on which connecting portions of the exhaust-gasupstream side end portions to the head flange.

EFFECT OF THE INVENTION

In the collecting part structure of the exhaust manifold of the presentinvention, the reinforcement member is composed of the two flat platesthat have the same length as the inner diameter of the collecting part,the flat plates being provided at their central positions with slitsfacing to each other, the flat plates being coupled with each other byengaging the slits with each other. The one plate with the slit at theexhaust-gas upstream side is arranged parallel with the straight line onwhich the connecting portions of the exhaust-gas upstream side endportions to the head flange. Each of the flat plates is only bent bystress due to thermal expansion of the branch pipes and thermal stressof the head flange in a longitudinal direction thereof so thatexhaust-gas upstream side end portions of the flat plates approach toeach other. The flat plates can be prevented from being twisted so thatexhaust-gas upstream side end portions thereof depart from each other ina reverse direction with respect to plate thickness directions of theplates. This is advantageous in strength. Further, the slit of the platethat is arranged parallel to the straight line is provided at theexhaust-gas upstream side of the plate, so that defects, such as stressconcentration at the slit and cracks at its periphery, can be avoided.As a result, strength can be easily increased to resist against thestress concentration at the exhaust-gas downstream side end portions ofthe branch pipes and their peripheral portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention willbecome apparent as the description proceeds when taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is an entire front view showing an exhaust manifold to which acollecting part structure of an exhaust manifold of an embodimentaccording to the present invention is applied;

FIG. 2 is an entire right side view showing the exhaust manifold towhich the collecting part structure of the exhaust manifold of theembodiment according to the present invention is applied;

FIG. 3 is a cross sectional view taken along a line S3-S3 in FIG. 1;

FIG. 4A is an exploded view showing a reinforcement member that is usedin the first embodiment, and FIG. 4B is a perspective view of thereinforcement member thereof;

FIG. 5A and FIG. 5B are views illustrating how to assemble thereinforcement member of the first embodiment;

FIG. 6A and FIG. 6B are views illustrating how to assemble branch pipesand the reinforcement member that are used in the first embodiment; and

FIG. 7 is a bottom view showing exhaust-gas downstream side end portionsof the exhaust manifold of the embodiment where a collecting part isremoved.

DESCRIPTION OF REFERENCE NUMBERS

-   S1, S2 slit-   X1, X2 welded portion-   1 head flange-   1 a connecting surface-   2, 3, 4, 5 branch pipe-   2 a, 3 a, 4 a, 5 a exhaust-gas downstream side end portion-   2 b, 3 b, 4 b, 5 b wall portion (that contacts with a reinforcement    member)-   6 collecting part-   6 a exhaust-gas upstream side end portion-   7 catalyst substrate-   8 catalytic converter-   9 reinforcement member-   10, 11 flat plate-   10 a, 11 a cut-off portion-   20 assembly jig-   20 a cut-off portion

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment according to the present invention will bedescribed with reference to the accompanying drawings.

First Embodiment

Hereinafter, a first embodiment will be described.

FIG. 1 is an entire front view showing an exhaust manifold to which acollecting part structure of an exhaust manifold of the first embodimentaccording to the present invention, FIG. 2 is a right side view of thesame, FIG. 3 is a cross sectional view taken along a line S3-S3 in FIG.1, FIG. 4A is an exploded view showing a reinforcement member of thefirst embodiment, and FIG. 4B is a perspective view showing the same.

FIG. 5A and FIG. 5B are views illustrating how to assemble thereinforcement member of the first embodiment, FIG. 6A and FIG. 6B areviews illustrating how to assemble branch pipes and the reinforcementmember, and FIG. 7 is a bottom view illustrating exhaust-gas downstreamside end portions of the exhaust manifold of the first embodiment wherea collecting part thereof is removed.

As shown in FIG. 1 and FIG. 2, the collecting part structure of theexhaust manifold of the first embodiment mainly includes a head flange 1that is connected with a not-shown engine, four branch pipes 2 to 5 thatare respectively connected with cylinders of the engine through the headflange 1, a collecting part 6 that is formed like a circular cylinder,and a catalytic converter 8 that is connected with the collecting part 6and contains catalyst substrate 7.

As shown in FIG. 1 to FIG. 7, connecting portions, of the four branchpipes 2 to 5, to the head flange 1 are arranged in line on a straightline Al.

On the other hand, as shown in FIG. 3, exhaust-gas downstream side endportions of the branches 2 to 5 are formed to have a cross section ofquadrant circle, and they are contained in an exhaust-gas upstream sideend portion 6 a of the collecting part 6 in a state where theexhaust-gas downstream side end portions of the branches 2 to 5 arecollected to form a circular cross section.

In addition, the reinforcement member 9 is provided among theexhaust-gas downstream side end portions of the branches 2 to 5.

Specifically, as shown in FIG. 4A and FIG. 4B, the reinforcement member9 is composed of two flat plates 10 and 11. Each of which has a lengthL1 that is approximately equal to an inner diameter of the collectingpart 6, and they are provide at central positions on opposed sidesthereof with slits S1 and S2, respectively. The flat plates 10 and 11are joined by engaging the slits S1 and S2 with each other to form likea cross shape.

In addition, both end portions of the flat plate 10 is formed at anexhaust-gas upstream side thereof with cut-out portions 10 a, while oneend portion of the flat plate 11 is formed at an exhaust-gas upstreamside thereof with a cut-off portion 11 a.

In a case where the flat plates 10 and 11 are fixed with each other, theflat plate 10 is engaged with an assembly jig 20, and then the flatplate 11 is engaged with the assembly jig 20. In this assembly, the flatplates 10 and 11 are prevented from being assembled in a wrong statethereof, because three cut-off portions 20 a that are formed on theassembly jig 20 correspond to the cut-off portions 10 a and 11 a of theflat plates 10 and 11. Incidentally, the flat plates 10 and 11 may befixed with each other by welding.

In addition, as shown in FIG. 6, wall portions 2 b to 5 b of the branchpipes 2 to 5 and the reinforcement member 9 are fixed with each other atwelded portions X1, as shown in FIG. 3, in a state where thereinforcement member 9 is disposed among the exhaust-gas downstream sideend portions 2 a to 5 a and it slightly projects toward a collectingpart 6 side.

In this state, the flat plate 11, which is formed with the slit S2 atthe exhaust-gad upstream side thereof, is set parallel to a line A1,namely on a line A2 that is parallel to the line A1, on which connectingportions of the branch pipes 2 to 5 that are connected with the headflange 1 are aligned on a connecting surface 1 a of the head flange 1.

Further, as shown in FIG. 3, the branch pipes 2 to 5 are inserted intothe exhaust-gas upstream side end portion 6 a together with thereinforcement member 9, and then outer circumferential surfaces of thebranches 2 to 5 are fixed to the collecting part 6 together with a partof the reinforcement member 9 at welded portions X2.

In the thus-constructed collecting part structure of the exhaustmanifold, exhaust gas flows in the collecting part 6 from the cylindersof the engine through the branch pipes 2 to 5, and then it is dischargedinto the catalytic converter 8.

In this operation, the head flange 1 thermally expands mainly in alongitudinal direction thereof due to heat of the exhaust gas, since theconnecting portions of the branch pipes 2 to 5 are arranged on thestraight line L1. As a result, its thermal stress acts on the branchpipes 2 to 5 in a direction where the exhaust-gas downstream side endportions 2 a to 5 a of the branch pipes 2 to 5 are separated from eachother outwardly in a longitudinal direction thereof.

Accordingly, since the flat plate 11, the slit S2 of which is providedat the exhaust-gas upstream side, is aligned on the line A2 that isparallel to the line A1 on which the connecting portions of the branchpipes 2 to 5 on the connecting surface 1 a of the head flange 1 arearranged, the thermal stress acts on the flat plate 11 only in adirection where the flat plate 11 is bent in directions indicated byarrows B1 and B2, without stress acting thereon so that the upstreamside both end portions of the flat plate 11 are twisted in reversedirections. Therefore, the plate 11 is advantageous in strength. Inaddition, when these bending forces acts, it becomes easy to avoid thestress that is concentrated at the slit S2 to tear the flat plate 11 atthe slit S2, because the slit S2 is formed at the exhaust-gas upstreamside of the flat plate 11 and there is no slit at the exhaust-gasdownstream side thereof. Further, there is no twisting stress thattwists the exhaust-gas upstream side end portions of the flat plate 10,which is arranged in perpendicular to the flat plate 11. Additionally,the bending stress acts in the directions indicated by B1 and B2, andaccordingly it approximately does not act on the slit S1. This isadvantageous in strength to the flat plate 10. Thus, there is no dangerin compression buckling of the flat plate 10 due to the thermal stress,and strength can be improved at peripheral portions of the exhaust-gasdownstream side end portions 2 a to 5 a of the branch pipes 2 to 5.

As described above, in the collecting part structure of the exhaustmanifold of the first embodiment, the exhaust manifold includes the fourbranch pipes 2 to 5, the collecting part 6 and the reinforcement member9. Exhaust-gas upstream side end portions of the four branch pipes 2 to5 are connected with the head flange 1 on the straight line, whileexhaust-gas downstream side end portions thereof are formed to have thecross section of the quadrant circle. The collecting part 6 collects andcontains the exhaust-gas downstream side end portions 2 a to 5 a of thebranch pipes to form the circular cross section. The reinforcementmember 9 is disposed among the exhaust-gas downstream side end portions2 a to 5 a of the branch pipes 2 to 5 to fix the exhaust-gas downstreamside end portions to the collecting part 6, and the reinforcement member9 has the two flat plates 10 and 11 with the same length L1 as an innerdiameter of the collecting part 6. The flat plates 10 and 11 areprovided at the central positions with slits S1 and S2 facing to eachother to be joined like the cross shape. The one flat plate 11, of theflat plates 10 and 11, that is formed with the slit S2 at an exhaust-gasupstream side thereof is arranged parallel with the straight line A1 onwhich the connecting portions of the exhaust-gas upstream side endportions to the head flange 1. Therefore, the exhaust-gas upstream sideboth end portions of the flat plates 10 and 11 can be prevented frombeing twisted in the reverse direction, which is advantageous instrength. As a result, the strength can be easily increased to resistthe stress concentration at the exhaust-gas downstream side end portions2 a to 5 a and their peripheral portions.

While the embodiment has been explained above, the present invention isnot limited to the above-described embodiment, and its design changesand modifications are contained in the present invention as long as theydo not depart from the subject-matter of the present invention.

For example, as explained above, the flat plate 11 that is formed withthe slit S2 at the exhaust-gas upstream side is arranged parallel to theconnecting surface 1 a of the head flange 1 in the first embodiment,while it is preferable that an exhaust-gas upstream side slit be formedon one of the flat plates 10 and 11 which is arranged in a state wherethe one is closer to parallel to the connecting surface la of the headflange 1. This case can also obtain the effects of the presentinvention.

1. A collecting part structure of an exhaust manifold including fourbranch pipes in which exhaust-gas upstream side end portions thereof areconnected with a head flange on a straight line, exhaust-gas downstreamside end portions thereof being formed to have a cross section of aquadrant circle; a collecting part that collects and contains theexhaust-gas downstream side end portions of the branch pipes to form acircular cross section; and a reinforcement member that is disposedamong the exhaust-gas downstream side end portions of the branch pipesto fix the exhaust-gas downstream side end portions to the collectingpart, the reinforcement member having two flat plates with the samelength as an inner diameter of the collecting part, the flat platesbeing provided at central positions with slits facing to each other tobe joined like a cross shape, the collecting part structurecharacterized in that one flat plate, of the flat plates, that is formedwith a slit at an exhaust-gas upstream side thereof is arranged parallelwith the straight line on which connecting portions of the exhaust-gasupstream side end portions to the head flange.